Altitude compensated vacuum amplifier

ABSTRACT

A mechanical device is located between the carburetor spark port and distributor breaker plate servo the device being fed by vacuum reservoir. The device provides a modulated vacuum control signal to the distributor breaker plate servo which is a function of spark port vacuum and the vehicle&#39;&#39;s altitudinal location by means of a pressure sensitive valving means operatively connected to an aneroid. The vacuum reservoir is charged by connection with the intake manifold, and a temperature responsive member may be added so that the vacuum control signal will be responsive to manifold pressure when the engine is subject to predetermined adverse temperature conditions. By placing a restriction means betweeen the reservoir and the mechanical device gradual changes in spark advance settings is accomplished during light vehicle accelerations, and upon rapid recovery of subsequent momentary decelerations; during times of heavy acceleration the vacuum control signal is vented to atmosphere through the valving means, thereby quickly lowering the spark advance setting to avoid engine detonation.

Stts net [191 11] 3,2,743 [451 Aug. 13, 1974 Primary ExaminerLaurence M. Goodridge Assistant Examiner-Ronald E. Cox Attorney, Agent, or Firm-Remy J. Van Ophem [57] STRACT A mechanical device is located between the carburetor spark port and distributor breaker plate servo the device being fed by vacuum reservoir. The device provides a modulated vacuum control signal to the distributor breaker plate servo which is a function of spark port vacuum and the vehicles altitudinal location by means of a pressure sensitive valving means operatively connected to an aneroid. The vacuum reservoir is charged by connection with the intake manifold, and a temperature responsive member may be added so that the vacuum control signal will be responsive to manifold pressure when the engine is subject to predetermined adverse temperature conditions. By placing a restriction means betweeen the reservoir and the mechanical device gradual changes in spark advance settings is accomplished during light vehicle accelerations, and upon rapid recovery of subsequent momentary decelerations; during times of heavy acceleration the vacuum control signal is vented to atmosphere through the valving means, thereby quickly lowering the spark advance setting to avoid engine detonation.

12 Claims, 3 Drawing Figures 50 mg/NE TEMPW/U'Ufi 1%,, MAN/FOLD P 60 4/1? FLOW can/7 0; VACUUM S-IVSOR SEA/50R sewsaa l f 4 7/ TUDE Sen 50R i I R'SERVO/R 90 "L P (an/777cm /0 Asses/way 4%.

V4UUM SERVO DISTRIBUTOR m PATENTED AUG] 3 I974 SHEET 2 [IF 3 I PATENTED 31974 3.828.743

SHEET 3 BF 3 a: :20 r 220 x// P 25/4 111 M 25 ALTITUDE COMPENSATED VACUUM AMPLIFIER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to an engine spark timing control system. More particularly, it relates to an apparatus that provides good operating performance as well as fuel economy by providing a spark advance vacuum control signal which is a function of both the absolute ambient pressure and engine speed.

2. Brief Description of the Prior Art Most present day motor vehicles have some sort of a vacuum servo automatically controlling the advance or retard setting of the engine distributor breaker plate as a function of carburetor spark port vacuum to provide good engine performance as well as fuel economy during the different operating conditions of the engine. These vacuum servos, in their simplest form, generally consist of a housing divided into atmospheric pressure and vacuum chambers by a flexible diaphragm connected to the distributor breaker plate. The diaphragm and breaker plate are normally spring biased to the lowest advance or retard spark timing setting, and carburetor spark port vacuum normally urges the diaphragm in a spark timing advance direction upon opening of the carburetor. throttle valve in an engine speed increasing direction.

With the above construction, during rapid acceleration, the drop in vacuum at the carburetor spark port permits atmospheric pressure acting on the opposite side of the servo diaphragm to immediately move the distributor breaker plate to a lower advance setting, to one that is best to meet engine performance requirements. On the other hand, however, upon return to normal operation and gradual reacceleration or deceleration of the engine, an increase in vacuum at the carburetor spark port causes an immediate return movement of the vacuum servo diaphragm to a higher engine spark timing advance setting. This provides a longer burning time for the fuel mixture before the optimum top or near top dead center position of the piston is attained, generally providing the most desirable operation. However, this longer time permits the build up to higher combustion temperatures and pressures, which are undesirable insofar as the production of oxides of nitrogen and other undesirable elements are concerned.

It will be seen, therefor, that the conventional spark timing control systems generally provide good performance and fuel economy, but do not necessarily mini mize the output of undesirable exhaust gas elements.

Other systems are known such as the type shown in U.S. Pat. No. 3,606,871 which were an improvement over the aforementioned devices. The above mentioned patent shows a mechanical device which includes a one-way check valve and an orifice in parallel flow circuits connected between the carburetor spark port and the vacuum servo mechanism. During rapid vehicle accelerations, the check valve unseats to provide a quick equilization of the pressure at the servo to the spark port vacuum, thereby lowering the spark advance setting to avoid detonation. Upon a momentary deceleration condition of operation, with a subsequent return toward its former operating condition, the orifice provides a slow build up of the vacuum level at the servo to equal that at the spark port so that the advance setting only slowly returns to normal. This results in lower peak' combustion temperatures and pressures and less emission of engine pollutants. However, the above referenced system is poor for fuel economy. The slower spark advance build up due to the orifice bleed of vacuum, causes late burning and generally at a point past optimum efficiency, i.e., into the expansion cycle of the engine.

An even later U.S. Pat. No. 3,698,366 overcame the disadvantageous function of the device above described by providing a rapid return of the spark timing advance setting to essentially its former level, after a momentary deceleration, to improve the fuel economy. This invention included a vacuum line between an intake manifold port and the distributor servo interconnected by a spring operated vacuum control valve which was in parallel flow relationship with a flow restriction in the vacuum line between the carburetor spark port and the distributor servo line.

None of the known prior art devices, however, are designed to carry on all of the advantageous features discussed above plus provide an amplified vacuum signal to the distributor which is a function of the spark port vacuum and the automobiles altitudinal location. That is, a standard automobile engine suffers degraded performance and possible increased emissions when operated at higher altitudes because of the reduced ambient air pressure causing a corresponding reduction in the spark port vacuum signal which was heretofore provided directly to the vacuum spark advance diaphragm actuator.

SUMMARY OF THE INVENTION Therefore, it is a primary object of the invention to provide an engine spark timing device that has the advantages of the conventional spark timing control system while minimizing the disadvantages by providing an altitude compensating control assembly consisting of an aneroid device connected directly to a vent valve and diaphragm actuator. As absolute pressure is reduced, the aneroid will produce a force output which requires a correspondingly higher distributor vacuum level to counteract the loss in carburetor spark port vacuum, the additional vacuum level being supplied by a vacuum source charged to a higher vacuum level than spark port vacuum. By proper selection of aneroid, diaphragm and vent valve areas, different ratios of altitude versus distributor vacuum amplification are possible. A restriction is disposed between the reservoir and the control assembly to permit a gradual change in the spark timing advance setting to a higher level upon acceleration. A temperature responsive valve means interconnects the intake manifold and the control assembly so that the distributor vacuum control signal will respond to manifold pressure instead of spark port vacuum when the ambient or engine temperature is below a predetermined level or engine temperature is above a predetermined level.

it is another object of the invention, to provide an engine spark timing control apparatus that provides correct spark timing setting during rapid vehicle accelerations; and, from light acceleration modes, a rapid return to the correct setting after a momentary deceleration, for good engine performance and fuel economy purposes, while at the same time providing the other necessary and desirable changes in spark timing to provide efficient engine operation.

It is another important object of this invention to provide an engine spark timing control apparatus which compensates for loss in the vacuum control signal to the engine distributor at high altitudes by increasing the vacuum control signal proportionally to the automobiles increase in altitude. In so doing any possible increase in emissions is prevented and the engine will not suffer degraded performance.

It is a further object of this invention to provide a vacuum control assembly for regulating the spark advance mechanism of an internal combustion engines distributor which is responsive to air fiow through the engine, and by means of a pressure sensitive valve connected to an aneroid and being in communication with a vacuum reservoir is operative to provide a vacuum control signal to the distributor which is a function of absolute ambient pressure and engine air flow.

Another object of this invention is to provide an altitude compensated vacuum amplifier which includes a temperature responsive means adapted to make the vacuum amplifier responsive to intake manifold pressure instead of carburetor spark port pressure when the engine is subject to predetermine adverse temperature conditions.

Other objects, features and advantages of the invention will become more apparent upon reference to the succeeding detailed description thereof, and to the drawings illustrating a preferred embodiment and one alternative embodiment thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of the engine spark timing control system.

FIG. 2 schematically illustrates a partially crosssectional view of an engine spark timing system embodying my invention.

FIG. 3 schematically illustrates a partial crosssectional view of the control assembly an alternative embodiment of an engine spark timing system embodying my invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a logic or block diagram of the inventive system. The control assembly has several inputs including the pressure signal P. generated by the engine air flow sensor 20, pressure signal P, representing the pressure in the reservoir 30 and a mechanical force F provided by the altitude sensor 40. In one mode of operation the pressure signal P is supplied to the control assembly 10 by a temperature control sensor 50. Both the temperature control sensor 50 and the reservoir 30 are fed or charged by the engines intake manifold through the manifold vacuum sensor 60. A check valve 70 disposed between reservoir 30 and vacuum sensor 60 insures that the vacuum level in the reservoir is always maintained when intake manifold vacuum decreases. A restriction member 80 between reservoir 30 and the control assembly 10 insures that pressure signal P, is gradually communicated to the control assembly. Another restriction member 90 disposed between the air flow sensor and the control assembly 10 insures that the pressure signal P,, is not lost to atmosphere through the engine air flow sensor under conditions which will be described below. The control assembly 10 is operative to sum the input P, and F,, and provide a vacuum control signal P, to the vacuum servo 100, P, being supplied by P,.. The vacuum servo 100 ultimately controls the movement of the distributor 110 by means of the mechanical force F,,.

FIG. 2 shows, schematically, only those portions of an internal combustion engine that are normally associated with the engine distributor spark timing setting control; such as, for example, a carburetor 21, a distributor breaker plate 111, and a vacuum servo 100 to control the movement of breaker plate 111. The control assembly 10 is connected to the vacuum servo 100 by means of a line 102 and to the carburetor 21 by means of a line 22.

More specifically, carburetor 21 is shown as being of the downdraft type having the usual air-fuel induction passage 23 with an atmospheric air inlet 24 at one end and connected to the engine intake manifold 25 at the opposite end. Passage 23 contains the usual fixed area venturi 26 and a throttle valve 27. The latter is rotatably mounted on a part of the carburetor body across passage 23 in a manner to control the flow of air fuel mixture into the intake manifold. Fuel would be inducted in the usual manner from a nozzle, not shown, projecting into or adjacent venturi 26 in a known manner.

Throttle valve 27 is shown in its engine idle speed position essentially closing induction passage 23, and is rotatable to a nearly vertical position essentially unlocking passage 23. A spark port 28 is provided at a point just above the idle position of throttle valve 27, to be traversed by the throttle valve during its part throttle opening movements. This will change the vacuum level in spark port 28 as a function of the rotative position of the throttle valve, the spark port reflecting essentially atmospheric pressure in the air inlet 24 upon closure of the throttle valve. An intake manifold vacuum sensing port is also provided, for a purpose to be described.

As stated previously, the distributor 110 includes a breaker plate 111 that is pivotally mounted at 112 on a stationary portion of the distributor, and moveable with respect to cam 113. The latter has six peaks 114 corresponding to the number of engine cylinders. Each of the peaks cooperates with the follower 115 of a breaker point set 116 to make or break the spark connection in a known manner for each one-sixth, in this case, rotation of cam 113. Pivotal movement of breaker plate 111 in a counter clockwise spark retard setting direction, or in a clockwise spark advance setting, is provided by an actuator 101 slidably extending from vacuum servo 100.

Servo may be of a conventional construction. It has a hollow housing 103 whose interior is divided into an atmospheric pressure chamber 104 and a vacuum chamber by an annular flexible diaphragm 106. The diaphragm is fixedly secured to actuator 101, and is biased in a rightward retard direction by a compression spring 107. Chamber 104 has an atmospheric or ambient pressure vent, not shown, while the chamber 105 is connected by a bore, not shown, to line 102.

During engine-off and other operating conditions to be described, atmospheric pressure exists on both sides of the diaphragm 106, permitting spring 107 to force the actuator 101 to the lowest advance or a retard setting position. Application of vacuum to chamber 105 moves diaphragm 106 and actuator 101 toward the left to an engine spark timing advance position, by degree as a function of the change in vacuum level.

Although only a single diaphragm servo 100 is illustrated, it will be clear that it is within the scope of the invention to connect line 102 to the primary or advance chamber of a dual diaphragm servo of the type which is commonly known in the art.

The control assembly or summation means includes a housing 11 having a plurality of passages connected thereto, including passage 1112 and 22. A diaphragm 12 is fixedly secured to housing 11 and is operative to move in a vertical direction relative to the drawing. Diaphragm 12 divides housing 11 into two chambers, 13 and 14, chamber 13 being in communication with spark port 28 through passage 22, and chamber 14 being in communication with reservoir 30 through passage 31 and vacuum servo 100 through passage 102. A valve stem 16 is fixedly secured to the pressure responsive diaphragm 12 and to a vent valve 15. Valve is adapted to move toward and away from its valve seat 17, valve seat 17 separating chamber 14 from atmospheric pressure P which is admitted to housing 11 through a filter 18. The relative pressures or vacuum levels in chamber 13 and chamber 14 will tend to equalize through a modulation of the vent valve 15. That is, if the vacuum in chamber 13 increases thereby pulling valve 15 into contact with valve seat 17,

additional vacuum will be communicated to chamber 14 from reservoir 30 until the resultant forces on both sides of diaphragm 12 are equal. Valve 15 will then begin to modulate or move toward and away from valve seat 17 to maintain this equilibrium through the admission of atmospheric pressure. Should the absolute pressure in chamber 13 increase and diaphragm 12 move upwardly, the absolute pressure in chamber 14 will be correspondingly increased by venting atmospheric air into chamber 14 through vent valve 15 until equilibrium is once again obtained.

A restriction means 80 is disposed in passage 31 which interconnects reservoir 30 and the control assembly 10 thereby assuring that the'vacuum signal P which is communicated to the vacuum servo 100 will increase relatively slowly for reasons discussed below.

The vacuum level in the reservoir 30, which serves as the vacuum source for the control signal P is maintained by the vacuum developed in the intake manifold 25, sensed by the manifold vacuum sensor 60 and communicated to reservoir 30 through passage 71. A spring biased check valve 70 disposed within passage 71 is designed to open whenever the vacuum level of the intake manifold is greater than the vacuum level in the reservoir 311 and to close whenever the vacuum level in the intake manifold drops below the vacuum signal P, of the reservoir 30. One skilled in the art will appreciate that other means such as the use of an air pump may be used to charge the reservoir or vacuum source to a level greater than spark port vacuum P however, the practical approach is to use the available source, i.e., intake manifold vacuum which in the advent of closed throttle operation develops a vacuum signal P, sufficient for any vacuum demands required of this system.

A temperature responsive valve means 50 intercon nects chamber 13 of control assembly 10 with the intake manifold 25 by means of passage 72 connected between member 511 and passage 71, and passage 51 connected between member 50 and the housing 11 of the control assembly 10. Passage 51 has two extensions 51a leading to a first valve seat 52 and passage 51b leading to a second valve seat 53 within the housing 54- of the temperature control sensor 50. Two cantilevered bimetallic members 55 and 56 are secured to housing 54 by conventional means such as brazing and are operative to move toward and away from valve seats 52 and 53 respectively. One skilled in the art will appreciate that any temperature responsive device may be employed such as a bimetal snap action disc or a melted wax element. These valves were designed as two-way rather than three-way valves to avoid undue complexity and hysteresis normally associated with three-way valves that would perform the required function. Element 55 is adapted by suitable means, not shown, to sense the engine, engine compartment or ambient temperature and will move away from valve seat 52 opening chamber 13 to the intake manifold when the engine or ambient temperature drops below a predetermined level. Element 56 on the other hand is connected by suitable means, not shown, directly to the engine block and senses the temperature of the engine coolant and is operative to move away from valve seat 53 thereby opening chamber 13 to the intake manifold when the engine coolant temperature exceeds a predetermined level.

A flow restriction means 90 is disposed in the carburetor spark port line 22 and is sized to provide the manifold signal P, to the chamber 13 of the control assembly 10 (when either temperature valve 52 or valve 53 is open) with only minor degradation of signal level. That is, restrictor 90 prevents the vacuum signal P to be lost to atmosphere through carburetor spark port 28. The orifice or restrictor 90 however is sized to be large enough to transmit the spark port signal to chamber 13 with little delay during all normal modes of operation.

The altitude sensor 10 may be one of the commonly known aneroids which are used in aircraft altimeters and barometers. These aneroids are available commercially, for example, from such companies as Kollsman Instrument Corporation. The aneroid 40 is shown fixedly secured to the housing 11 of the control assembly 10 and having a mechanical linkage 41 which is fixedly secured to the vent valve 15. It is understood under typical operation of such a device, that as the atmospheric pressure surrounding the aneroid decreases such as by increasing the altitude of the aneroid, the bellows mechanism of the aneroid will expand. In this case as the aneroid 40 expands during an increase in altitude, it produces a force F which reacts directly on valve 15 in a downward direction.

OPERATION OF THE PREFERRED EMBODIMENT Prior to starting the engine, the servo chambers 1M and 105, and chambers 13 and 14 of the control assembly 10 are equalized and essentially atmospheric pressure.

Assuming that the vehicle is at sea level and that the engine ambient temperature is below F., the engine starting condition will be described. When the engine is started, the bimetallic element will be displaced from the valve seat 52 so that the intake manifold sensed by element 60 will be communicated through the intake manifold will not be lost due to the restriction device 90 disposed in the passage 22. During this mode of operation reservoir 30 will be charged to the maximum intake manifold pressure developed, and since .the pressure responsive diaphragm 12 will be drawn downwardly by the vacuum of the intake manifold, valve 15 will be closed against the valve seat 17 and the vacuum control signal P will equal P, which equals P,,,. The restriction'member 80 between the reservoir 30 and control assembly will allow the vacuum control signal P, to gradually build thereby gradually advancing the spark setting to the vacuum servo 100. Thus, due to the connection to the intake manifold through the temperature responsive member 50 the spark is advanced during this cold start condition.

Assuming the vehicle is still located at sea level and that the ambient temperature is above the predetermined cut-off level and that the engine coolant temperature is below the predetermined cut-off level, that is, both valves 52 and 53 are closed, operation of the inventive system will be described for the idle speed condition. During idle, the throttle body 27 is closed and the spark port 28 is essentially at atmospheric pressure. However, the intake manifold is at a significant vacuum level and therefor reservoir 30 is being charged by the intake manifold due to the open check valve 70. Since the vacuum in chamber 13 is essentially at zero inches of mercury and since chamber 4 is at some previously attained vacuum level, diaphragm 12 will translate upwardly thereby opening vent valve admitting atmospheric pressure to chamber 14 until P also equals zero inches of mercury vacuum which in turn translates diaphragm 106 of the vacuum servo 100 to the right to a spark retard setting. Thus a zero spark advance setting is accomplished during the idle speed condition.

As the vehicle begins to accelerate check valve 70 will close since the manifold vacuum level will drop below the previous vacuum level of reservoir 30. As the throttle valve 28 opens and the vacuum level at spark port 28 begins to build, this vacuum level is communicated to the diaphragm 12 by means of passage 22 thereby drawing diaphragm 12 downward closing valve 15 against its seat 17. When valve 15 closes the vacuum supply in reservoir 30 is admitted to chamber 14 through the restriction 80 until the vacuum level in the chamber 13 equals the vacuum in chamber 14. Thus the vacuum control signal P will eventually equal P i.e., spark port vacuum; breaker plate 111 will begin to move in a clockwise direction due to the actuator 101 which is moved by the diaphragm 106 and the vacuum communicated to chamber 105 of the vacuum servo 100 causing a gradual spark advance setting. As soon as P equals P vent valve 15 will begin to modulate in order to maintain equilibrium on both sides of diaphragm 12.

As the vehicle decelerates during normal operation the vacuum at the intake manifold 25 increases, eventually opening check valve 70 and charging reservoir 30 to the higher intake manifold vacuum level. Simultaneously the carburetor spark port vacuum signal P. decreases thereby translating the diaphragm 12 upwardly opening vent valve 15; the vacuum in chamber 105 of the vacuum servo 100 is gradually vented to atmosphere through valve 15 thus allowing for a gradual reduction of spark advance.

The controlled decay of the spark advance signal, on gradual deceleration, offers yet another advantage. When the vehicle is operating at a steady state speed and is subjected to a momentary deceleration, the spark advance signal has only been partially destroyed since vent valve 15 controls the decrease of vacuum signal P at a rate which is proportional to the decrease in spark port vacuum P Therefor, upon a light reacceleration, the control signal P will still be near the desired position for this particular speed and load. This minimizes depreciation of fuel economy.

At a steady state cruise condition, P will equal 1. and the spark will be at the desired advance setting. Due to the modulation of the vent valve during this equilibrium, the reservoir will eventually reach the same vacuum level as the distributor vacuum signal. The reservoir 30, however, will be recharged each time the throttle is closed and the manifold vacuum is thereby increased.

When the vehicle is operating at a steady state speed and is suddenly subject to a heavy or wide open throttle acceleration, the vacuum at the carburetor spark port 28 will drop thereby translating diaphragm 12 upwardly quickly opening vent valve 15 dumping the pressure signal P to atmosphere. This action then permits an unrestricted flow of air at atmospheric pressure toward the distributor servo chamber 105 and returns the spark setting to the normal lower position for that particular speed and load condition to prevent engine detonation.

When the vehicle is operated at higher altitudes the carburetor spark port vacuum signal is not great enough to yield the full vacuum advance signal P required for optimum operating conditions. Thus,- a means is required for producing a vacuum control signal P which is a finite amount greater than P at higher altitudes. This finite amount is determined by the force F produced by the aneroid 40. That is, as the vehicle increases in altitude the bellows of the aneroid 40 will expand causing a greater pressure to be placed on the top of vent valve 15 by the mechanical linkage 41 which in turn allows a greater vacuum to be communicated to chamber 14 from reservoir 30 before the vent valve 15 will open and modulate. Once P multiplied times the effective area of diaphragm 12 (A equals F plus P times A,,, vent valve 15 will modulate at this new level of equilibrium.

Assume for example that the vehicle is at a cruise speed at some predetermined altitude wherein the aneroid is expanded and placing some finite force F upon the top of vent valve 15, and that the reservoir 30 is charged to some predetermined level greater than P, either by the intake manifold or some other source. The servo vacuum control signal P will equal the spark port signal P. plus an amount which will equal the force F since the vent valve 15 will not open and begin to modulate until the reservoir supplies a vacuum to chamber 14 which is equal to said sum. Thus the loss in carburetor spark port vacuum P, at such altitude is effectively compensated by amplifying the vacuum control signal by means of a vacuum source and an aneroid device. By careful selection of aneroid, diaphragm and vent valve areas, different ratios of altitude versus distributor vacuum amplification are possible. One skilled in the art will appreciate the simplicity and reliability of the disclosed vacuum amplifier which accomplishes all of the previously stated objectives.

Although not specifically described note that should the engine overheat, for example on a hot summer day in heavy traffic, bimetallic plate 56 will open upon reaching some predetermined high temperature thereby admitting intake manifold pressure to chamber 13 causing the vacuum to advance from its zero spark advance engine idle state. This will cause the engine to run at a higher speed causing the engine fan to cool the engine coolant to a more desirable temperature.

DESCRIPTION OF AN ALTERNATIVE EMBODIMENT Referring to FIG. 3 an alternative embodiment of the control assembly 10 is shown with those parts similar to the preferred embodiment shown with the same reference numerals. All other parts of the system not shown are identical with those described for FIG. 2. Passage 31 extends into housing 11 and has formed at its terminal end a valve seat 201. Valve stem 16 is adapted to cooperate with two spring biased poppet valve assemblies 210 and 220 which assemblies cooperate with valve seat 17 and valve seat 201 respectively. Three dynamic seals 231, 232, and 233 are adapted to cooperate with poppet valve 210, passage 31' and poppet valve 220 in order to prevent any loss in vacuum signal. Dynamic seals 231 and 233 also serve as valves cooperating with valve seat 17 and valve seat 201 respectively. A spring 241 is retained by a spring retainer 242 fixedly secured to valve stem 16' and biases valve seal 231 into engagement with valve seat 17. A spring 251 retained by a spring retainer 252 which is fixedly secured to stem 16, biases valve-seal 233 into engagement with a valve shaft portion 253. A disc 260 is fixedly secured to valve stem 16' at a location which will insure that valve 233 will be closed against valve seat 201 before member 260 lifts valve 231 off its valve seat 17.

Operation of the alternative embodiment is essentially the same as was described for the preferred embodiment with one major exception. Notice that as diaphragm 12 translates upwardly as the vacuum signal P decreases, valve 233 will close against its seat 2111 thereby blocking off the vacuum signal P, from reservoir before disc 260 engages with the valve 231. Thus the vacuum control signal P will equal F and the vacuum source P, will be shut off. If P,, increases diaphragm 12 will translate downwardly opening valve 233 and admitting a higher vacuum level to the chamber 14. If P, should further decrease in value valve 233 will close and disc 260 will lift valve 231 from seat 17 until the vacuum level on chamber 14 equals P,

It is to be noted that the vacuum supply P, will only be ported to the vacuum servo assembly 1011 when required thereby improving the system efficiency by not wasting the vacuum supply stored in the reservoir 30. This particular feature is an improvement over the preferred embodiment which modulates the required vacuum level by continuously venting through vent valve 15, which under certain conditions will gradually deplete the vacuum stored in the reservoir 30. However, the three-way valve of the alternative embodiment has inherent hysteresis clue to the dynamic shaft seals and is obviously more complex.

The operation of aneroid and the alternative embodiment is identical to that described above for the preferred embodiment, in that under higher altitude operating conditions aneroid 40 and the mechanical linkage 41 prevents the shaft 16 acting through disc 2611 to open valve 231 to atmosphere until the vacuum control signal P times A equals P times A plus the force F, of the aneroid 40.

From the above, it will be seen that the invention provides for increased spark advance during high altitude operation to compensate for the inherent loss in spark port vacuum at such altitudes, thereby improving engine performance and decreasing unfavorable emissions. Further, the invention provides for spark ad vance by slow build up in vacuum through the restriction means so that lower peak combustion temperatures and pressures are obtained, resulting in less exhaust emission of pollutants regardless of vehicle altitude. It will also be seen that for engine performance, the servo vacuum signal P, is quickly dumped to atmosphere through vent valve 15 and valve 233 of the two control assemblies 10 and 10' respectively thereby quickly lowering the advance setting of the distributor to prevent spark detonation. It will also be seen, that upon a temporary deceleration condition of operation, from light accelerating modes, reacceleration to return to or toward the previous setting provides a rapid re covery of the distributor breaker plate to essentially its former setting.

Although only one preferred embodiment and one alternative embodiment of the invention have been shown and described in detail it will be understood that changes may be made in the design and arrangement of the parts without departing from the spirit of the invention.

I claim:

1. A vacuum control system for regulating the spark advance mechanism of an internal combustion engine 5 distributor comprising:

means for generating a vacuum signal responsive to air flow through the engine;

a vacuum source maintained at a vacuum level greater than said vacuum signal;

means for sensing the altitudinal location of the engine and adapted to generate a mechanical force in response thereto; and means for summing said vacuum signal and said mechanical force and adapted to provide a vacuum control signal to the spark advance mechanism equal to said summation, said summing means operatively interconnecting said engine air flow sensing means, said vacuum source and said altitude sensing means so that said spark advance mechanism will receive a control signal which is a function of absolute ambient pressure and engine speed. 2. The combination as claimed in claim 1 including further:

means for communicating the engine intake manifold pressure to said summing means; and

temperature responsive means disposed between said communication means and said summing means or making said control signal responsive to manifold pressure when the engine is subject to predetermined temperature conditions.

3. The combination as claimed in claim 2 wherein the temperature responsive means comprises a housing having a plurality of passages extending therefrom at least one of said passages connected to the intake manifold and at least one other of said passages connected to said summing means;

at least one valve means associated with at least one of said passages, said valve means adapted to terminate communication of the pressure of the intake manifold to said summing means; and

at least one bimetallic temperature responsive member adapted to cooperate with said valve means so that in response to predetermined temperature conditions said bimetallic member will open said valve means thereby permitting said intake manifold vacuum to communicate with said summation means.

4. The combination as claimed in claim 1 wherein the means for generating a pressure signal responsive to air flow through the engine comprises:

an engine carburetor having an induction passage containing a port located above the idle speed position of a throttle valve controlling flow through the passage and subject to the depression in the carburetor as a function of the movement of the throttle valve from its idle speed position.

5. The combination as claimed in claim 1 wherein said vacuum source comprises:

a housing having passage means extending therefrom, said passage means disposed so as to interconnect said reservoir with said engine intake manifold and said summing means, said passage means having a check valve means disposed therein so that the vacuum in said reservoir is maintained at a level equal to or greater than the vacuum level in said engine intake manifold.

6. The combination as claimed in claim 5 including further restriction means disposed in said passage means between said reservoir and said summing means operative to provide limited communication between said reservoir and said summing means so that said vacuum control signal increases gradually.

7. The combination as claimed in claim 1 wherein said means for sensing the altitudinal location of the engine comprises:

an aneroid operatively connected to said summing means.

8. The combination as claimed in claim 1 wherein said summation means comprises;

a housing having a plurality of passages extending therefrom;

diaphragm means operatively disposed within said housing and exposed on one side to said engine air flow vacuum signal, and on the other side to said vacuum source and the spark advance mechanism; and

valve means disposed within said housing for venting said other side of said diaphragm means to atmosphere, said valve means being operatively connected to said altitude sensing means and said diaphragm means so that said valve means will translate as a function of the summation of the forces on said diaphragm means and said altitude sensing means.

9. The combination as claimed in claim 8 wherein said valve means comprises:

a valve stem fixedly secured to said diaphragm and said altitude sensing means;

a vent valve fixedly secured to said stem intermediate of said diaphragm and said altitude sensing means; and

valve seat means adapted to cooperate with said vent valve, said valve seat means and said vent valve being operative to vent said other side of said diaphragm to atmosphere.

10. The combination as claimed in claim 8 wherein said valve means comprises:

a valve stem fixedly secured to said diaphragm means and said altitude sensing means;

a first valve fixedly secured to said stem and operative when closed to terminate communication between said vacuum source said other side of said diaphragm means; and

a second valve fixedly secured to said stern and operative to vent said other side of said diaphragm to atmosphere when said first valve is closed.

11. In an automobile internal combustion engine having an ignition distributor and pressure responsive control means connected to the distributor for advancing and retarding it in accordance with engine speed, a vacuum control assembly connected to said pressure responsive control means and comprising:

vacuum storage means connected to said control assembly;

an altitude sensor adapted to provide a variable force as a function of the vehicles altitudinal location;

pressure sensitive means responsive to engine air flow; and

control means operatively interconnecting said pressure sensitive means and said altitude sensor so that a modulated vacuum signal is communicated to the automobiles distributor from said vacuum storage means in response to engine air flow and vehicle altitude.

12. The combination as claimed in claim 11 including further a temperature control assembly interconnecting said pressure sensitive means and the engine intake manifold so that in response to predetermined low ambient and high engine temperature said pressure sensitive means will respond to intake manifold pressure and vehicle altitude.

, NITED STATES PATENT OFFICE CERTIFICATE OF CDRRECTION Patent No. 3,828,743 Dated Au r; 13, 1974 Inventofls) George Ludwig It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Abstract Line 14: Rep1ace the word "betweeen" with the word between Co'lumn 7:

Line 30: Refflace the number "4" with the number 14 Signed and sealed this 29th day of October 1974.

(SEAL) Attest MCCOY M. GIBSON JR. c. MARSHALL DANN Arresting Officer Commissioner of- Patents 

1. A vacuum control system for regulating the spark advance mechanism of an internal combustion engine''s distributor comprising: means for generating a vacuum signal responsive to air flow through the engine; a vacuum source maintained at a vacuum level greater than said vacuum signal; means for sensing the altitudinal location of the engine and adapted to generate a mechanical force in response thereto; and means for summing said vacuum signal and said mechanical force and adapted to provide a vacuum control signal to the spark advance mechanism equal to said summation, said summing means operatively interconnecting said engine air flow sensing means, said vacuum source and said altitude sensing means so that said spark advance mechanism will receive a control signal which is a function of absolute ambient pressure and engine speed.
 2. The combination as claimed in claim 1 including further: means for communicating the engine intake manifold pressure to said summing means; and temperature responsive means disposed between said communication means and said summing means or making said control signal responsive to manifold pressure when the engine is subject to predetermined temperature conditions.
 3. The combination as claimed in claim 2 wherein the temperature responsive means comprises a housing having a plurality of passages extending therefrom at least one of said passages connected to the intake manifold and at least one other of said passages connected to said summing means; at least one valve means associated with at least one of said passages, said valve means adapted to terminate communication of the pressure of the intake manifold to said summing means; and at least one bimetallic temperature responsive member adapted to cooperate with said valve means so that in response to predetermined temperature conditions said bimetallic memBer will open said valve means thereby permitting said intake manifold vacuum to communicate with said summation means.
 4. The combination as claimed in claim 1 wherein the means for generating a pressure signal responsive to air flow through the engine comprises: an engine carburetor having an induction passage containing a port located above the idle speed position of a throttle valve controlling flow through the passage and subject to the depression in the carburetor as a function of the movement of the throttle valve from its idle speed position.
 5. The combination as claimed in claim 1 wherein said vacuum source comprises: a housing having passage means extending therefrom, said passage means disposed so as to interconnect said reservoir with said engine intake manifold and said summing means, said passage means having a check valve means disposed therein so that the vacuum in said reservoir is maintained at a level equal to or greater than the vacuum level in said engine intake manifold.
 6. The combination as claimed in claim 5 including further restriction means disposed in said passage means between said reservoir and said summing means operative to provide limited communication between said reservoir and said summing means so that said vacuum control signal increases gradually.
 7. The combination as claimed in claim 1 wherein said means for sensing the altitudinal location of the engine comprises: an aneroid operatively connected to said summing means.
 8. The combination as claimed in claim 1 wherein said summation means comprises: a housing having a plurality of passages extending therefrom; diaphragm means operatively disposed within said housing and exposed on one side to said engine air flow vacuum signal, and on the other side to said vacuum source and the spark advance mechanism; and valve means disposed within said housing for venting said other side of said diaphragm means to atmosphere, said valve means being operatively connected to said altitude sensing means and said diaphragm means so that said valve means will translate as a function of the summation of the forces on said diaphragm means and said altitude sensing means.
 9. The combination as claimed in claim 8 wherein said valve means comprises: a valve stem fixedly secured to said diaphragm and said altitude sensing means; a vent valve fixedly secured to said stem intermediate of said diaphragm and said altitude sensing means; and valve seat means adapted to cooperate with said vent valve, said valve seat means and said vent valve being operative to vent said other side of said diaphragm to atmosphere.
 10. The combination as claimed in claim 8 wherein said valve means comprises: a valve stem fixedly secured to said diaphragm means and said altitude sensing means; a first valve fixedly secured to said stem and operative when closed to terminate communication between said vacuum source said other side of said diaphragm means; and a second valve fixedly secured to said stem and operative to vent said other side of said diaphragm to atmosphere when said first valve is closed.
 11. In an automobile internal combustion engine having an ignition distributor and pressure responsive control means connected to the distributor for advancing and retarding it in accordance with engine speed, a vacuum control assembly connected to said pressure responsive control means and comprising: vacuum storage means connected to said control assembly; an altitude sensor adapted to provide a variable force as a function of the vehicles altitudinal location; pressure sensitive means responsive to engine air flow; and control means operatively interconnecting said pressure sensitive means and said altitude sensor so that a modulated vacuum signal is communicated to the automobile''s distributor from said vacuum storage means in response to engine air flow and vehicle altitude.
 12. The combination as claimed in claim 11 including further a temperature control assembly interconnecting said pressure sensitive means and the engine intake manifold so that in response to predetermined low ambient and high engine temperature said pressure sensitive means will respond to intake manifold pressure and vehicle altitude. 